System and method for heater vessel wall temperature reduction

ABSTRACT

An apparatus, system, and method for heating fluidic material includes a sleeve positioned within a housing, with at least a portion of at least one heating element passing through the sleeve and an annulus defined by an exterior surface of the sleeve and an interior surface of the housing. A flow restrictor is positioned within the housing to control the flow of fluidic material through the sleeve relative to the flow of fluidic material through the annulus, the fluidic material through the annulus having a higher linear velocity than the flow through the sleeve.

FIELD OF THE INVENTION

The present invention relates in general to process heaters and in particular to an apparatus, system, and method to control the vessel wall temperature of a process heater.

BACKGROUND OF THE INVENTION

A process heater is a heater that heats a process fluid, which can be a gas such as methane or air, prior to that process fluid flowing into a subsequent process. An example of a process heater is a heater that heats methane before the methane flows into a power generation furnace. Typical electric process heaters include electric heater elements, or rods, positioned inside a tubular pressure vessel. The process fluid flows through the tubular pressure vessel. Electric current through a filament within the heater element causes the heater element to produce heat, which is transferred to the fluid as the fluid flows past the element. Unfortunately, heat from the heater element is also radiated to the vessel wall. The hot vessel walls can decrease the operational life of the process heater. To overcome the effects of the heat, the vessel wall must be made of a sufficiently thick material and, in some cases, additional insulation is required. Sometimes the vessel must be made of an exotic material to withstand the heat. The thick vessel wall, the choice of material, and the insulation can each increase the cost and the weight of the process heater. It is desirable to transfer heat from the heater elements to the process fluid without inadvertently radiating so much heat to the vessel wall.

SUMMARY OF THE INVENTION

An apparatus, system, and method for heating fluidic material includes a sleeve positioned within a housing, and an annulus defined by an exterior surface of the sleeve and an interior surface of the housing. At least a portion of the heating elements pass through the sleeve. As the fluidic material flows through the heater, a portion of the fluidic material flows through the sleeve and a portion of the fluidic material flows through the annulus. A flow restrictor is positioned within the housing to control the flow of fluidic material through the sleeve relative to the flow of fluidic material through the annulus. In embodiments, the fluidic material flowing through the annulus has a higher linear velocity than the flow through the sleeve.

In an embodiment of the apparatus for heating a fluid material, the apparatus includes a tubular housing that defines a passageway, wherein an upstream end of the passageway is adapted to be operably coupled to an inlet stream of fluidic material and a downstream end of the passageway comprises an outlet. A sleeve can be positioned concentrically within the passageway and define an annulus between the sleeve and an inner diameter of the housing, the sleeve having a sleeve passage therethrough, the annulus and the sleeve passage each being in communication with the passageway so that when fluidic materials flow through the passageway, a portion of the fluidic material flow through the annulus and another portion of the fluidic materials flow through the sleeve passage. One or more heating elements can be positioned at least partially within the sleeve and, because the sleeve is within the outer housing, the one or more heater elements are positioned within the outer housing. A flow restrictor can be positioned to control flow through the sleeve relative to the flow through the annulus.

In embodiments, the flow restrictor reduces the flow of fluidic materials through the sleeve passage so that the linear velocity of the fluidic materials in the annulus is greater than the linear velocity of the fluidic materials in the sleeve passage. In embodiments, the flow restrictor includes a cone having a large opening at a first end and a small opening at a second end, the small opening being smaller than the large opening. The cross sectional area of the large opening can be at least two times greater than the cross sectional area of the small opening. In embodiments, the cross sectional area of the large opening is about 1.5 to 5 times greater than the cross sectional area of the small opening. The large opening can be connected to an end of the sleeve and the small opening can be nearer the downstream end of the passageway than the larger opening. The flow restrictor can be nearer the downstream end of the passageway than the sleeve. In embodiments, the fluid flowing through the annulus is turbulent.

In embodiments, the flow restrictor includes a cone having a frustoconical shape, and fluid flowing through the sleeve flows through an interior of the cone and fluid flowing through the annulus flows along an exterior of the cone. In embodiments, the flow restrictor can include a variable flow restrictor, the variable flow restrictor being adapted to change the volume of fluid flow through the sleeve passage in response to conditions within the tubular housing. In embodiments, those conditions within the tubular housing can include a temperature of the tubular housing, a temperature of the fluidic material at the outlet, or the flow rate of the fluidic material.

In embodiments, the cross sectional area of the sleeve passage is about 5-10 times greater than the cross sectional area of the annulus. In embodiments, the cross sectional area of the sleeve passage is at least six times greater than the cross sectional area of the annulus.

In embodiments of a method for heating fluidic material, the method includes the steps of placing a sleeve inside a housing and creating an annulus therebetween; positioning at least one heating element within the housing so that at least a portion of the heating element passes through the sleeve; and flowing a fluidic material through the housing, a portion of the fluidic material flowing through the annulus and a portion of the fluidic material flowing through the sleeve, the portion of fluid flowing through the annulus having a higher linear velocity than the portion of fluid flowing through the sleeve. Embodiments can include the step of the step of positioning a flow restrictor in the housing, the flow restrictor restricting the flow of fluidic material through the sleeve.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial sectional environmental view of a process heater having an inner sleeve and flow restrictor in accordance with an embodiment of the invention.

FIG. 2 is a side sectional view of the process heater of FIG. 1.

FIG. 3 is a sectional view, taken along the 3-3 line of FIG. 2.

FIG. 4 is a perspective view of a heater element support of the process heater of FIG. 1.

FIG. 5 is a perspective view of the flow restrictor of the process heater of FIG. 1.

FIG. 6 is a side sectional view of a process heater having an inner sleeve and variable flow restrictor in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a process heater 100 is a heater for heating fluidic material. The fluidic material can be a fluid such as methane, air, nitrogen, hydrogen, other types of gas, or liquid. Process heater 100 includes a pressure vessel having a housing 102, which can be tubular, that defines a passageway through which the fluidic media can flow. Housing 102 can be a cylindrical body having a vessel wall with an inner vessel wall surface and an outer vessel wall surface. Upstream end cap 106 and downstream end cap 108 can be placed on the ends of housing 102. The length of housing 102 is considerably greater than its diameter. As one of skill in the art will appreciate, housing 102 can have other shapes and end configurations.

Housing 102 has an upstream end 110 connected to fluid inlet 112, and a downstream end 114 connected to fluid outlet 116. The fluidic media flows into process heater 100 through inlet 112, is heated as it flows through housing 102 from upstream end 110 toward downstream end 114, and flows out through fluid outlet 116.

Referring to FIGS. 1 and 2, a sleeve 120, which can be tubular, is positioned concentrically within housing 102. The outer diameter of sleeve 120 is less than the inner diameter of housing 102 so that there is an annulus 122 between sleeve 120 and an inner diameter of housing 102. Sleeve 120 has a sleeve passage 124 therethrough. Annulus 122 and sleeve passage 124 (FIG. 2) are each in communication with the passageway defined by housing 102. As best shown in FIG. 2, when fluidic media flows through the passageway defined by housing 102, a portion of the fluidic media 104A flows through annulus 122 and another portion of the fluidic media 104B flows through sleeve passage 124. In the embodiment shown in FIG. 1, annulus 122 or sleeve passage 124 are the only pathways through the passageway defined by housing 102, so all of the fluidic media flows through annulus 122 or sleeve passage 124.

As best shown in FIG. 3, the cross sectional area of sleeve passage 124 can be larger than the cross sectional area of annulus 122. In embodiments, the cross sectional area of sleeve passage 124 is about 2-20 times greater than the cross sectional area of annulus 122. In embodiments, the cross sectional area of sleeve passage 124 is about 3-15 times greater than the cross sectional area of annulus 122. In embodiments, the cross sectional area of sleeve passage 124 is about 5-10 times greater than the cross sectional area of annulus 122. In embodiments, the cross sectional area of sleeve passage 124 is more than about 6 times greater than the cross sectional area of annulus 122.

Referring now to FIGS. 1-4, a plurality of electric heater elements 128 extend longitudinally within housing 102, with at least a portion of each heater element 128 extending through at least a portion of sleeve passage 124 of sleeve 120. Heater elements 128 can be conventional elements, each having a metal tube containing an electrical resistance wire electrically insulated from the metal tube. In embodiments, heater elements 128 are U-shaped, each having terminal ends 130 mounted within a connector housing 132 and a u-shaped portion 134 at the opposite end. As one of skill in the art will appreciate, heater element supports, such as the support 135 shown in FIG. 4, can be located within sleeve 120, including at terminal end 130, near u-shaped portion 134, and at various locations therebetween, to support each of the heater elements 128. As shown in FIG. 4, heater elements 128 can each pass through and be supported by element orifice 136 of heater element support 135. Fluidic media 104B can flow through fluid orifices 137 of heater element support 135. Referring back to FIG. 2, a shielded portion 138 of each heater element 128 is the portion of heater element 128 located within sleeve 120, and an unshielded portion 140 of each heater element 128 is the portion of heater element 128 located axially outside of sleeve 120. As one of skill in the art will appreciate, each heater element 128 can include a filament (not shown) that produces heat in response to electric current. Each heater element 128 can also include a conductive pin, or rod (not shown), that conducts electric current from terminal end 130 to the filament. The pin has substantially less resistance than the filament and, thus, does not produce a significant amount of heat. In embodiments, the filament extends only through the shielded portion 138 of heater element 128, and the pin extends at least the length of unshielded portion 140. Therefore, substantially all of the heat produced by each heater element 128 is produced within sleeve passage 124.

A power controller 142 supplies power via wires 144 to electrical heater elements 128. A plurality of wires 144 can be used, with each wire 144 being connected to one or more heater elements 128 (for the sake of illustration, only one such wire 144 is shown in FIG. 1). Power controller 142 can vary the power in response to a temperature setpoint and the temperature sensed by a temperature sensor (not shown in FIGS. 1 and 2) that is able to detect the temperature of the fluidic media after the fluidic media flows past heater elements 128. The temperature sensor (not shown in FIGS. 1 and 2) can be, for example, in contact with the fluidic media downstream of heater elements 128, or otherwise located near or downstream from outlet 116.

Referring to FIGS. 1 and 2, a flow restrictor 148 is positioned at an end of the sleeve 120 to alter the flow passing through sleeve passage 124. Flow restrictor 148 reduces the flow of fluidic materials through sleeve passage 124 so that the linear velocity of the fluidic materials in annulus 122, which is not restricted by flow restrictor 148, is greater than the linear velocity of the fluidic materials through sleeve passage 124. Flow restrictor 148 can be any of a variety of devices that restrict or obstruct the flow of fluidic media 104B through sleeve passage 124. In embodiments, flow restrictor 148 can include one or more apertures therethrough, where the combined cross-sectional area of the apertures is less than the cross sectional area of at least a portion of sleeve passage 124 (FIG. 2).

Referring to FIG. 5, flow restrictor 148 can be, for example, a cone, having a frustoconical shape, with a large opening 150 at one end and a small opening 152 at the other end. In the embodiment shown in FIG. 2, large opening 150 (FIG. 5) is connected to the downstream end of sleeve 120 and the small opening 152 is positioned downstream from large opening 150. In embodiments, the cross sectional area of large opening 150 is at least two times greater than the cross sectional area of small opening 152. In embodiments, the cross sectional area of the large opening is about 1.5 to 5 times greater than the cross sectional area of small opening 152.

The portion of fluid flowing through annulus 122 flows past the outer diameter surface of flow restrictor 148 as the fluid flows from the upstream end toward the downstream end of housing 102. In embodiments where flow restrictor 148 has a frustoconical shape and is connected to the downstream end of sleeve 120, the space between the outer diameter of flow restrictor 148 and the inner diameter of housing 102 is a restrictor annulus 154 having a cross sectional area that becomes increasingly larger when moving from the upstream end toward the downstream end. As shown in FIG. 2, the fluidic media 104A flowing through restrictor annulus 154 is turbulent as it flows past flow restrictor 148, the turbulent flow being shown as fluidic media 104A′. Fluidic media 104A can be turbulent as it flows through annulus 154, the turbulence being caused by, for example, flow conditions such as the increased velocity of fluidic media 104A that results from restrictor 148.

In embodiments, flow restrictor 148 can be a variable flow restrictor. A variable flow restrictor can, for example, reduce or increase the size of small opening 152. The variable flow restrictor can change the volume of fluid flow through the sleeve passage in response to conditions within process heater 100. Those conditions can include, for example, the temperature of housing 102, the temperature of the fluidic material at outlet 116, the flow rate of the fluidic material through process heater 100, and the flow ratio sleeve 120 and annulus 122. For example, if the wall of housing 102 becomes too hot, the variable flow restrictor can decrease the flow through the flow restrictor 148 and, thus, increase the velocity of flow through annulus 122. If the heat provided by heater elements 128 is relatively low such that housing 102 remains relatively cool, then the variable flow restrictor can increase the size of small opening 152 to allow a greater percentage of flow through sleeve 120 relative to the flow through annulus 122.

Referring now to FIG. 6, process heater 160 is shown. Process heater 160 includes housing 162, sleeve 164 positioned within housing 162 and defining annulus 166 between housing 162 and sleeve 164. Heater elements 168 are positioned within housing 162 such that at least a portion of heater elements 168 are positioned within sleeve 164. Fluidic media 170 flows through housing 162 from an upstream end toward a downstream end. A portion of fluidic media 170 flows through sleeve 164 and another portion of fluidic media 170 flows through annulus 166. The portion of fluidic media 170 flowing through annulus 166 flows in the same direction as the portion of fluidic media flowing through sleeve 164.

Variable flow restrictor 172 is positioned at an end of sleeve 164. Variable flow restrictor 172 can restrict the flow of fluidic media 170 flowing through sleeve 164 and, thus, cause the fluidic media flowing through annulus 166 to flow at a higher velocity than the fluidic media flowing through sleeve 164. In embodiments, variable flow restrictor can include orifice 174 and plunger 176. In the embodiment shown in FIG. 5, orifice 174 is an outlet of sleeve 164 through which fluidic media 170 from sleeve 164 must flow. Plunger 176 has a conical shape that becomes progressively wider when moving from the upstream end toward the downstream end. Plunger 176 can be concentrically positioned within orifice 174, and can move axially in the upstream and downstream directions. Plunger 176 is shown in solid lines in a high flow position. Plunger 176 is shown as plunger 176′, in dashed lines, in a low flow position. Gap 178 is the space between the inner diameter of orifice 174 and the outer surface of plunger 176. As a person of ordinary skill in the art will recognize, plunger 176′ extends further into orifice 174 in the low flow position than in the high flow position, and, thus, gap 178 is smaller in the low flow position than in the high flow position.

In embodiments, actuator 180 is connected to plunger 176 and can be used to move plunger 176 between the high flow and the low flow positions. Actuator 180 can include, for example, a threaded shaft extending through an end of housing 162. An operator can manually rotate the threaded shaft of actuator 180 to extend and retract plunger 176 relative to orifice 174. In embodiments, actuator 180 can include a controller 182 in communication with, for example, an electric motor, a solenoid, or a piston, that can be used to extend or retract plunger 176. For example, a temperature sensor 184 can send a temperature signal to the controller of actuator 180. In response to the temperature signal, actuator 180 can move plunger 176 to permit more or less flow through orifice 174 and, thus, through sleeve 164. In embodiments, actuator 180 can include a thermal expansion element that expands in response to heat. The thermal expansion element can, for example, begin to expand when the temperature of the thermal expansion unit exceeds a preselected value, and continue to expand in proportion to the temperature. The expansion can cause plunger 176 to move toward the low flow position. When the temperature is reduced, the thermal expansion element can contract, thus causing plunger 176 to move back to the high flow position. One of skill in the art will appreciate that variable flow restrictor 180 is not limited to embodiments of a plunger obstructing an orifice. Other embodiments can be used such as, for example, a damper that variably covers an opening or a cone having movable petals that reduce or enlarge the size of the opening of the cone.

In the event that process heater 160 is running hot, and thus housing 162 is getting hot, variable flow restrictor 172 can reduce the flow through sleeve 164. That reduction can cause increased flow through annulus 166. That increased flow results in more heat being transferred from the exterior of sleeve 164 to the fluidic media in annulus 166 and, thus, reduce the amount of heat transferred from sleeve 164 to housing 162. When process heater 160 is producing less heat, variable flow restrictor 172 can flow more fluidic media through sleeve 164 and, thus, reduce the relative flow through annulus 166.

Referring back to FIGS. 1-5, in operation, fluidic media 104 flows in through inlet 112 into housing 102. A portion of fluidic media 104, shown as fluidic media 104B, flows into and through sleeve 120. Heater elements 128 heat fluidic media 104B as it flows through sleeve passage 124. Fluidic media 104B flows through flow restrictor 148 so that the now-heated fluidic media 104B flows out through small opening 152.

Another portion of fluidic media 104, identified as fluidic media 104A, flows through annulus 122 between the outer diameter of sleeve 120 and the inner diameter of housing 102. In embodiments, fluidic media 104A can be turbulent as it flows through annulus 122. Such turbulence can facilitate greater heat transfer between the outer diameter of sleeve 120 and fluidic media 104A. Similarly, fluidic media 104B can be turbulent as it flows through sleeve passage 124, which can facilitate greater heat transfer between heater elements 128 and fluidic media 104B. In embodiments, fluidic media 104A flows in parallel to fluidic media 104B, such that fluidic media 104 flows through either sleeve passage 124 or annulus 122, each in the same direction, but no portion of fluidic media 104 flows through both sleeve passage 124 and annulus 122. In embodiments, an insignificant portion of fluidic media 104 may flow through both sleeve passage 124 and annulus 122, but substantially all of fluidic media 104 flows through one or the other, and not both, of sleeve passage 124 and annulus 122. In the embodiment shown in FIG. 2, fluidic media 104A flows through annulus 122 and then flows past the outer diameter of flow restrictor 148. Fluidic media 104A can be turbulent in restrictor annulus 154. The turbulent flow is identified as fluidic media 104A′ in FIG. 2.

After flowing past flow restrictor 148, fluidic media 104A merges with fluidic media 104B to form a mixed flow, the mixed flow identified as fluidic media 104C in FIG. 2. Because of flow restrictor 148, fluidic media 104A has a higher linear flow velocity than fluidic media 104B and, thus, fluidic media 104A is in contact with sleeve 120 for less time than fluidic media 104B is in contact with heater elements 128. While some heat is transferred from sleeve 120 to fluidic media 104A, fluidic media 104A is substantially cooler than fluidic media 104B because fluidic media 104A does not come into contact with heater elements 128 either before or after flowing through annulus 122.

Upon mixing, fluidic media 104C has a generally homogenous temperature. The cross sectional area of annulus 122 is substantially smaller than the cross sectional area of sleeve passage 124, so the flow volume of fluidic media 104A, through annulus 122, is substantially smaller than the flow volume of fluidic media 104B, through sleeve passage 124—in spite of the higher flow velocity of fluidic media 104A relative to the flow velocity of fluidic media 104B. Because the flow volume of fluidic media 104A is substantially less than the flow volume of fluidic media 104B, fluidic media 104A does not substantially cool fluidic media 104B when those two fluids mix as fluidic media 104C. Furthermore, because heat from sleeve 120 is transferred to fluidic media 104A and moved downstream, less heat is transferred to housing 102 than would be transferred if fluidic media 104A was not flowing through annulus 122 or if fluidic media 104A had a lower velocity.

Experimental Data

Experiments were conducted using an experimental embodiment of a process flow heater 100. In the embodiment, the housing 102 is 6″ diameter schedule 40 pipe. Twelve u-shaped heater elements 128 are used, thus presenting 24 heating rods within heater 100. Sleeve 120 has an outer diameter of 5.7″ and an inner diameter of 5.5″. The cross sectional area of annulus 122 is 3.4 square inches, and the cross sectional area of sleeve passage 124 is 21.6 square inches. Flow restrictor 148 has a large opening 150 with an inner diameter substantially similar to the inner diameter of sleeve 120, and a small opening 152 having a 2″ diameter. The cross sectional area of large opening 150 is 3.1 square inches and the cross sectional area of small opening 152 is 0.8 square inches.

Experimental data shows that the vessel wall temperature of housing 102 when using the sleeve 120 without the flow restrictor 148 was substantially the same as the vessel wall temperature of housing 102 with no sleeve. A sleeve without a flow restrictor does not significantly reduce the vessel wall temperature during sustained operation. One possible theory for this failure to reduce temperature is that there is insufficient flow in the annulus between the sleeve and the housing to overcome the effect of thermal radiation on the housing. In contrast, using both sleeve 120 and flow restrictor 148 resulted in a 40% temperature reduction at the vessel wall of housing 102.

Experimental data shows a substantial reduction in vessel wall temperature when sleeve 120 and flow restrictor 148 are used. The following Table 1 shows the conditions of the experiments:

TABLE 1 Conditions of the Experiments Experiment 1 - Air Experiment 2 - Methane Fluid: Air Methane Inlet Pressure: 5 psig 5 psig Flow: 1000 lb/hr 450 lb/hr Outlet Temp: 1000° F. 1000° F. Power Applied: 85 KW 85 KW Heater Bundle: 6″ pattern with 12 elements 6″ pattern with 12 elements

The following Table 2 shows the result of the Experiment 1 with and without sleeve 120 (tube).

TABLE 2 Experiment 1 Data Experiment 1 Air Smaller With Tube Hole Without Tube Results Internal External External Internal External OuterWall 1755 1727 1291 2341 2356 Max. Temp, ° F. Pressure Drop, 0.42 0.465 2.03 0.022 0.026 PSI Velocity, Max., 413 411 777 66 78 ft/s Element Max. 2042 2017 1875 2405 2439 Temp, ° F. Outlet Temp., 1184 1260 1201 1083 1145 ° F. Flow, lb/s 0.278 Heat Input, 85 KW Heat Density, 24.2 wsi Inlet Temp., 68.1 ° F. Outer Wall 586 629 1065 Temperature Reduction ° F.

As illustrated by table 2, the temperature of the internal surface of the outer wall was 586° F. lower when the sleeve and flow restrictor were used. The temperature of the external surface of the outer wall was 629° F. lower when the sleeve and flow restrictor were used. When a smaller outlet size was used (the “Smaller Hole”), the external surface temperature was 1065° F. lower than when no sleeve was used.

The following Table 3 shows the result of the Experiment 1 with and without sleeve 120 (tube).

TABLE 3 Experiment 2 Data Experiment 2 Methane With Tube Without Tube Results Internal External Internal External OuterWall Max. 1061 815 1630 1563 Temp, ° F. Pressure Drop, PSI 0.13 0.11 0.01 0.01 Velocity, Max., ft/s 298 275 50 57 Element Max. 1651 1466 1782 1764 Temp, ° F. Outlet Temp., ° F. 945 812 918 958 Flow, lb/s 0.125 Heat Input, KW 85 Heat Density, wsi 24.2 Inlet Temp., ° F. 68.1 Outer Wall 569 748 Temperature Reduction ° F.

As illustrated by table 3, the temperature of the internal surface of the outer wall was 569° F. lower when the sleeve and flow restrictor were used. The temperature of the external surface of the outer wall was 748° F. lower when the sleeve and flow restrictor were used.

It is understood that variations may be made in the above without departing from the scope of the invention. While specific embodiments have been shown and described, modifications can be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments as described are exemplary only and are not limiting. Many variations and modifications are possible and are within the scope of the invention. Furthermore, one or more aspects of the exemplary embodiments may be omitted or combined with one or more aspects of the other exemplary embodiments. Accordingly, the scope of protection is not limited to the embodiments described, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. 

1. An apparatus for heating a fluid material, the apparatus comprising: a tubular housing defining a passageway therethrough and having an upstream end adapted to be operably coupled to an inlet stream of fluidic material and a downstream end having an outlet; a sleeve positioned concentrically within the passageway and defining an annulus between the sleeve and an inner diameter of the housing, the sleeve having a sleeve passage therethrough, the annulus and the sleeve passage each being in communication with the passageway so that when fluidic materials flow through the passageway, a portion of the fluidic material flows through the annulus and another portion of the fluidic materials flow through the sleeve passage; one or more heating elements positioned within the outer housing with at least a portion of each of the one or more heating elements positioned within at least a portion of the sleeve; and a flow restrictor positioned to restrict the flow of the fluidic material through the sleeve passage.
 2. The apparatus according to claim 1, wherein the flow restrictor causes a linear velocity of the fluidic materials in the annulus is greater than a linear velocity of the fluidic materials in the sleeve passage.
 3. The apparatus according to claim 1, wherein the flow restrictor comprises one or more apertures therethrough, and wherein a combined cross-sectional area of the apertures is less than a cross sectional area of the sleeve passage.
 4. The apparatus according to claim 1, wherein the flow restrictor comprises a cone having a large opening at a first end and a small opening at a second end, the small opening being smaller than the large opening.
 5. The apparatus according to claim 1, wherein the flow restrictor is nearer the downstream end of the passageway than the sleeve.
 6. The apparatus according to claim 5, wherein the fluid flowing through the annulus becomes turbulent.
 7. The apparatus according to claim 1, wherein the flow restrictor comprises a cone having a frustoconical shape, and wherein fluid flowing through the sleeve flows through an interior of the cone and fluid flowing through the annulus flows along an exterior of the cone.
 8. The apparatus according to claim 1, wherein the flow restrictor comprises a variable flow restrictor, the variable flow restrictor being adapted to change the volume of fluid flow through the sleeve passage in response to conditions within the tubular housing.
 9. The apparatus according to claim 8, wherein the conditions within the tubular housing are selected from a group consisting of a temperature of the tubular housing, a temperature of the fluidic material at the outlet, and the flow rate of the fluidic material.
 10. The apparatus according to claim 1, wherein the flow restrictor comprises a variable flow restrictor having a thermal expansion element, the thermal expansion element expanding in response to increased temperature, the expansion causing the flow restrictor to reduce flow through the sleeve passage.
 11. The apparatus according to claim 1, wherein the cross sectional area of the sleeve passage is about 5-10 times greater than the cross sectional area of the annulus.
 12. The apparatus according to claim 1, wherein the cross sectional area of the sleeve passage is at least six times greater than the cross sectional area of the annulus.
 13. An apparatus for heating a fluidic material, the apparatus comprising: a tubular housing that defines a passageway, wherein an upstream end of the passageway is adapted to be operably coupled to an inlet stream of fluidic material and a downstream end of the passageway comprises an outlet; a sleeve positioned concentrically within the passageway and defining an annulus between the sleeve and an inner diameter of the housing, the sleeve having a sleeve passage therethrough, the annulus and the sleeve passage each being in communication with the passageway so that when fluidic materials flow through the passageway, a portion of the fluidic material flow through the annulus and another portion of the fluidic materials flow through the sleeve passage; one or more heating elements positioned within the outer housing so that at least a portion of each of the one or more heating elements extends through at least a portion of the sleeve passage; and a flow restrictor positioned to reduce the flow of fluidic materials through the sleeve passage so that the linear velocity of the fluidic materials in the annulus is greater than the linear velocity of the fluidic materials in the sleeve passage.
 14. The apparatus according to claim 13, wherein the flow restrictor comprises a cone having a large opening at a first end and a small opening at a second end, the small opening being smaller than the large opening.
 15. The apparatus according to claim 13, wherein the fluid flowing through the annulus becomes turbulent after flowing past the flow restrictor.
 16. The apparatus according to claim 13, wherein the flow restrictor comprises a variable flow restrictor, the variable flow restrictor being adapted to change the volume of fluid flow through the sleeve passage in response to conditions within the tubular housing.
 17. A method for heating fluidic material, the method comprising the steps of: (a) placing a sleeve inside a housing and creating an annulus therebetween; (b) positioning at least one heating element within the housing so that at least a portion of the heating element passes through the sleeve; and (c) flowing a fluidic material through the housing, a portion of the fluidic material flowing through the annulus and a portion of the fluidic material flowing through the sleeve, the portion of fluid flowing through the annulus having a higher linear velocity than the portion of fluid flowing through the sleeve.
 18. The method according to claim 17, wherein step (c) further comprises the step of positioning a flow restrictor in the housing, the flow restrictor restricting the flow of fluidic material through the sleeve.
 19. The method according to claim 17, wherein step (c) further comprises the step of reducing the flow of the fluidic materials through the sleeve in response to the temperature of the fluidic materials.
 20. The method according to claim 17, further comprising the step of merging the flow of fluidic material from the annulus with the flow of fluidic material from the sleeve. 